2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[HsTypes]{Abstract syntax: user-defined types}
8 HsType(..), HsUsageAnn(..), HsTyVarBndr(..),
9 , HsContext, HsPred(..)
10 , HsTupCon(..), hsTupParens, mkHsTupCon,
12 , mkHsForAllTy, mkHsUsForAllTy, mkHsDictTy, mkHsIParamTy
13 , getTyVarName, replaceTyVarName
16 , pprParendHsType, pprHsForAll, pprHsContext, pprHsTyVarBndr
18 -- Equality over Hs things
19 , EqHsEnv, emptyEqHsEnv, extendEqHsEnv,
20 , eqWithHsTyVars, eq_hsVar, eq_hsVars, eq_hsType, eq_hsContext, eqListBy
22 -- Converting from Type to HsType
23 , toHsType, toHsTyVar, toHsTyVars, toHsContext, toHsFDs
26 #include "HsVersions.h"
28 import Class ( FunDep )
29 import Type ( Type, Kind, PredType(..), UsageAnn(..), ClassContext,
30 getTyVar_maybe, splitFunTy_maybe, splitAppTy_maybe,
31 splitTyConApp_maybe, splitPredTy_maybe,
32 splitUsgTy, splitSigmaTy, unUsgTy, boxedTypeKind
34 import TypeRep ( Type(..), TyNote(..) ) -- toHsType sees the representation
35 import TyCon ( isTupleTyCon, tupleTyConBoxity, tyConArity, tyConClass_maybe )
36 import PrelInfo ( mkTupConRdrName )
37 import RdrName ( RdrName )
38 import Name ( toRdrName )
39 import OccName ( NameSpace )
40 import Var ( TyVar, tyVarKind )
41 import PprType ( {- instance Outputable Kind -}, pprParendKind )
42 import BasicTypes ( Arity, Boxity(..), tupleParens )
43 import Unique ( hasKey, listTyConKey, Uniquable(..) )
44 import Maybes ( maybeToBool )
49 This is the syntax for types as seen in type signatures.
52 type HsContext name = [HsPred name]
54 data HsPred name = HsPClass name [HsType name]
55 | HsPIParam name (HsType name)
58 = HsForAllTy (Maybe [HsTyVarBndr name]) -- Nothing for implicitly quantified signatures
62 | HsTyVar name -- Type variable
64 | HsAppTy (HsType name)
67 | HsFunTy (HsType name) -- function type
70 | HsListTy (HsType name) -- Element type
72 | HsTupleTy (HsTupCon name)
73 [HsType name] -- Element types (length gives arity)
75 -- these next two are only used in interfaces
76 | HsPredTy (HsPred name)
78 | HsUsgTy (HsUsageAnn name)
90 -----------------------
91 data HsTupCon name = HsTupCon name Boxity
93 instance Eq name => Eq (HsTupCon name) where
94 (HsTupCon _ b1) == (HsTupCon _ b2) = b1==b2
96 mkHsTupCon :: NameSpace -> Boxity -> [a] -> HsTupCon RdrName
97 mkHsTupCon space boxity args = HsTupCon (mkTupConRdrName space boxity (length args)) boxity
99 hsTupParens :: HsTupCon name -> SDoc -> SDoc
100 hsTupParens (HsTupCon _ b) p = tupleParens b p
102 -----------------------
103 -- Combine adjacent for-alls.
104 -- The following awkward situation can happen otherwise:
105 -- f :: forall a. ((Num a) => Int)
106 -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
107 -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
108 -- but the export list abstracts f wrt [a]. Disaster.
110 -- A valid type must have one for-all at the top of the type, or of the fn arg types
112 mkHsForAllTy (Just []) [] ty = ty -- Explicit for-all with no tyvars
113 mkHsForAllTy mtvs1 [] (HsForAllTy mtvs2 ctxt ty) = mkHsForAllTy (mtvs1 `plus` mtvs2) ctxt ty
115 mtvs1 `plus` Nothing = mtvs1
116 Nothing `plus` mtvs2 = mtvs2
117 (Just tvs1) `plus` (Just tvs2) = Just (tvs1 ++ tvs2)
118 mkHsForAllTy tvs ctxt ty = HsForAllTy tvs ctxt ty
120 mkHsUsForAllTy uvs ty = foldr (\ uv ty -> HsUsgForAllTy uv ty)
123 mkHsDictTy cls tys = HsPredTy (HsPClass cls tys)
124 mkHsIParamTy v ty = HsPredTy (HsPIParam v ty)
126 data HsTyVarBndr name
128 | IfaceTyVar name Kind
129 -- *** NOTA BENE *** A "monotype" in a pragma can have
130 -- for-alls in it, (mostly to do with dictionaries). These
131 -- must be explicitly Kinded.
133 getTyVarName (UserTyVar n) = n
134 getTyVarName (IfaceTyVar n _) = n
136 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
137 replaceTyVarName (UserTyVar n) n' = UserTyVar n'
138 replaceTyVarName (IfaceTyVar n k) n' = IfaceTyVar n' k
142 %************************************************************************
144 \subsection{Pretty printing}
146 %************************************************************************
148 NB: these types get printed into interface files, so
149 don't change the printing format lightly
152 instance (Outputable name) => Outputable (HsType name) where
153 ppr ty = pprHsType ty
155 instance (Outputable name) => Outputable (HsTyVarBndr name) where
156 ppr (UserTyVar name) = ppr name
157 ppr (IfaceTyVar name kind) = pprHsTyVarBndr name kind
159 instance Outputable name => Outputable (HsPred name) where
160 ppr (HsPClass clas tys) = ppr clas <+> hsep (map pprParendHsType tys)
161 ppr (HsPIParam n ty) = hsep [{- char '?' <> -} ppr n, text "::", ppr ty]
163 pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
164 pprHsTyVarBndr name kind | kind == boxedTypeKind = ppr name
165 | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
167 pprHsForAll [] [] = empty
169 -- This printer is used for both interface files and
170 -- printing user types in error messages; and alas the
171 -- two use slightly different syntax. Ah well.
172 = getPprStyle $ \ sty ->
173 if userStyle sty then
174 ptext SLIT("forall") <+> interppSP tvs <> dot <+>
178 ppr_context cxt <+> ptext SLIT("=>")
180 else -- Used in interfaces
181 ptext SLIT("__forall") <+> interppSP tvs <+>
182 ppr_context cxt <+> ptext SLIT("=>")
184 pprHsContext :: (Outputable name) => HsContext name -> SDoc
185 pprHsContext [] = empty
186 pprHsContext cxt = ppr_context cxt <+> ptext SLIT("=>")
188 ppr_context [] = empty
189 ppr_context cxt = parens (interpp'SP cxt)
193 pREC_TOP = (0 :: Int)
194 pREC_FUN = (1 :: Int)
195 pREC_CON = (2 :: Int)
197 maybeParen :: Bool -> SDoc -> SDoc
198 maybeParen True p = parens p
199 maybeParen False p = p
201 -- printing works more-or-less as for Types
203 pprHsType, pprParendHsType :: (Outputable name) => HsType name -> SDoc
205 pprHsType ty = ppr_mono_ty pREC_TOP ty
206 pprParendHsType ty = ppr_mono_ty pREC_CON ty
208 ppr_mono_ty ctxt_prec (HsForAllTy maybe_tvs ctxt ty)
209 = maybeParen (ctxt_prec >= pREC_FUN) $
210 sep [pp_header, pprHsType ty]
212 pp_header = case maybe_tvs of
213 Just tvs -> pprHsForAll tvs ctxt
214 Nothing -> pprHsContext ctxt
216 ppr_mono_ty ctxt_prec (HsTyVar name)
219 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2)
220 = let p1 = ppr_mono_ty pREC_FUN ty1
221 p2 = ppr_mono_ty pREC_TOP ty2
223 maybeParen (ctxt_prec >= pREC_FUN)
224 (sep [p1, (<>) (ptext SLIT("-> ")) p2])
226 ppr_mono_ty ctxt_prec (HsTupleTy con tys) = hsTupParens con (interpp'SP tys)
227 ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_ty pREC_TOP ty)
229 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
230 = maybeParen (ctxt_prec >= pREC_CON)
231 (hsep [ppr_mono_ty pREC_FUN fun_ty, ppr_mono_ty pREC_CON arg_ty])
233 ppr_mono_ty ctxt_prec (HsPredTy pred)
234 = maybeParen (ctxt_prec >= pREC_FUN) $
237 ppr_mono_ty ctxt_prec ty@(HsUsgForAllTy _ _)
239 sep [ ptext SLIT("__fuall") <+> brackets pp_uvars <+> ptext SLIT("=>"),
240 ppr_mono_ty pREC_TOP sigma
243 (uvars,sigma) = split [] ty
244 pp_uvars = interppSP uvars
246 split uvs (HsUsgForAllTy uv ty') = split (uv:uvs) ty'
247 split uvs ty' = (reverse uvs,ty')
249 ppr_mono_ty ctxt_prec (HsUsgTy u ty)
250 = maybeParen (ctxt_prec >= pREC_CON) $
251 ptext SLIT("__u") <+> pp_ua <+> ppr_mono_ty pREC_CON ty
254 HsUsOnce -> ptext SLIT("-")
255 HsUsMany -> ptext SLIT("!")
260 %************************************************************************
262 \subsection{Converting from Type to HsType}
264 %************************************************************************
266 @toHsType@ converts from a Type to a HsType, making the latter look as
267 user-friendly as possible. Notably, it uses synonyms where possible, and
268 expresses overloaded functions using the '=>' context part of a HsForAllTy.
271 toHsTyVar :: TyVar -> HsTyVarBndr RdrName
272 toHsTyVar tv = IfaceTyVar (toRdrName tv) (tyVarKind tv)
274 toHsTyVars tvs = map toHsTyVar tvs
276 toHsType :: Type -> HsType RdrName
277 toHsType ty = toHsType' (unUsgTy ty)
278 -- For now we just discard the usage
279 -- = case splitUsgTy ty of
280 -- (usg, tau) -> HsUsgTy (toHsUsg usg) (toHsType' tau)
282 toHsType' :: Type -> HsType RdrName
283 -- Called after the usage is stripped off
284 -- This function knows the representation of types
285 toHsType' (TyVarTy tv) = HsTyVar (toRdrName tv)
286 toHsType' (FunTy arg res) = HsFunTy (toHsType arg) (toHsType res)
287 toHsType' (AppTy fun arg) = HsAppTy (toHsType fun) (toHsType arg)
289 toHsType' (NoteTy (SynNote ty) _) = toHsType ty -- Use synonyms if possible!!
290 toHsType' (NoteTy _ ty) = toHsType ty
292 toHsType' ty@(TyConApp tc tys) -- Must be saturated because toHsType's arg is of kind *
293 | not saturated = generic_case
294 | isTupleTyCon tc = HsTupleTy (HsTupCon (toRdrName tc) (tupleTyConBoxity tc)) tys'
295 | tc `hasKey` listTyConKey = HsListTy (head tys')
296 | maybeToBool maybe_class = HsPredTy (HsPClass (toRdrName clas) tys')
297 | otherwise = generic_case
299 generic_case = foldl HsAppTy (HsTyVar (toRdrName tc)) tys'
300 maybe_class = tyConClass_maybe tc
301 Just clas = maybe_class
302 tys' = map toHsType tys
303 saturated = length tys == tyConArity tc
305 toHsType' ty@(ForAllTy _ _) = case splitSigmaTy ty of
306 (tvs, preds, tau) -> HsForAllTy (Just (map toHsTyVar tvs))
311 toHsPred (Class cls tys) = HsPClass (toRdrName cls) (map toHsType tys)
312 toHsPred (IParam n ty) = HsPIParam (toRdrName n) (toHsType ty)
314 toHsContext :: ClassContext -> HsContext RdrName
315 toHsContext cxt = [HsPClass (toRdrName cls) (map toHsType tys) | (cls,tys) <- cxt]
317 toHsUsg UsOnce = HsUsOnce
318 toHsUsg UsMany = HsUsMany
319 toHsUsg (UsVar v) = HsUsVar (toRdrName v)
321 toHsFDs :: [FunDep TyVar] -> [FunDep RdrName]
322 toHsFDs fds = [(map toRdrName ns, map toRdrName ms) | (ns,ms) <- fds]
326 %************************************************************************
328 \subsection{Comparison}
330 %************************************************************************
333 instance Ord a => Eq (HsType a) where
334 -- The Ord is needed because we keep a
335 -- finite map of variables to variables
336 (==) a b = eq_hsType emptyEqHsEnv a b
338 instance Ord a => Eq (HsPred a) where
339 (==) a b = eq_hsPred emptyEqHsEnv a b
341 eqWithHsTyVars :: Ord name =>
342 [HsTyVarBndr name] -> [HsTyVarBndr name]
343 -> (EqHsEnv name -> Bool) -> Bool
344 eqWithHsTyVars = eq_hsTyVars emptyEqHsEnv
348 type EqHsEnv n = FiniteMap n n
349 -- Tracks the mapping from L-variables to R-variables
351 eq_hsVar :: Ord n => EqHsEnv n -> n -> n -> Bool
352 eq_hsVar env n1 n2 = case lookupFM env n1 of
356 extendEqHsEnv env n1 n2
358 | otherwise = addToFM env n1 n2
360 emptyEqHsEnv :: EqHsEnv n
361 emptyEqHsEnv = emptyFM
364 We do define a specialised equality for these \tr{*Type} types; used
365 in checking interfaces.
369 eq_hsTyVars env [] [] k = k env
370 eq_hsTyVars env (tv1:tvs1) (tv2:tvs2) k = eq_hsTyVar env tv1 tv2 $ \ env ->
371 eq_hsTyVars env tvs1 tvs2 k
372 eq_hsTyVars env _ _ _ = False
374 eq_hsTyVar env (UserTyVar v1) (UserTyVar v2) k = k (extendEqHsEnv env v1 v2)
375 eq_hsTyVar env (IfaceTyVar v1 k1) (IfaceTyVar v2 k2) k = k1 == k2 && k (extendEqHsEnv env v1 v2)
376 eq_hsTyVar env _ _ _ = False
378 eq_hsVars env [] [] k = k env
379 eq_hsVars env (v1:bs1) (v2:bs2) k = eq_hsVars (extendEqHsEnv env v1 v2) bs1 bs2 k
380 eq_hsVars env _ _ _ = False
385 eq_hsTypes env = eqListBy (eq_hsType env)
388 eq_hsType env (HsForAllTy tvs1 c1 t1) (HsForAllTy tvs2 c2 t2)
389 = eq_tvs tvs1 tvs2 $ \env ->
390 eq_hsContext env c1 c2 &&
393 eq_tvs Nothing (Just _) k = False
394 eq_tvs Nothing Nothing k = k env
395 eq_tvs (Just _) Nothing k = False
396 eq_tvs (Just tvs1) (Just tvs2) k = eq_hsTyVars env tvs1 tvs2 k
398 eq_hsType env (HsTyVar n1) (HsTyVar n2)
401 eq_hsType env (HsTupleTy c1 tys1) (HsTupleTy c2 tys2)
402 = (c1 == c2) && eq_hsTypes env tys1 tys2
404 eq_hsType env (HsListTy ty1) (HsListTy ty2)
405 = eq_hsType env ty1 ty2
407 eq_hsType env (HsAppTy fun_ty1 arg_ty1) (HsAppTy fun_ty2 arg_ty2)
408 = eq_hsType env fun_ty1 fun_ty2 && eq_hsType env arg_ty1 arg_ty2
410 eq_hsType env (HsFunTy a1 b1) (HsFunTy a2 b2)
411 = eq_hsType env a1 a2 && eq_hsType env b1 b2
413 eq_hsType env (HsPredTy p1) (HsPredTy p2)
414 = eq_hsPred env p1 p2
416 eq_hsType env (HsUsgTy u1 ty1) (HsUsgTy u2 ty2)
417 = eqUsg u1 u2 && eq_hsType env ty1 ty2
419 eq_hsType env ty1 ty2 = False
423 eq_hsContext env a b = eqListBy (eq_hsPred env) a b
426 eq_hsPred env (HsPClass c1 tys1) (HsPClass c2 tys2)
427 = c1 == c2 && eq_hsTypes env tys1 tys2
428 eq_hsPred env (HsPIParam n1 ty1) (HsPIParam n2 ty2)
429 = n1 == n2 && eq_hsType env ty1 ty2
430 eq_hsPred env _ _ = False
433 eqUsg HsUsOnce HsUsOnce = True
434 eqUsg HsUsMany HsUsMany = True
435 eqUsg (HsUsVar u1) (HsUsVar u2) = u1 == u2
439 eqListBy :: (a->a->Bool) -> [a] -> [a] -> Bool
440 eqListBy eq [] [] = True
441 eqListBy eq (x:xs) (y:ys) = eq x y && eqListBy eq xs ys
442 eqListBy eq xs ys = False